Search

Galaxy cluster surveys will be a powerful probe of dark energy. At the same time, cluster abundance is sensitive to any non-Gaussianity of the primordial density field. It is therefore possible that non-Gaussian initial conditions might be misinterpreted as a sign of dark energy or at least degrade the expected constraints on dark energy parameters. To address this issue, we perform a likelihood analysis of an ideal cluster survey similar in size and depth to the upcoming South Pole Telescope survey and Dark Energy Survey. We analyze a model in which the strength of the non-Gaussianity is parameterized by the constant fNL; this model has been used extensively to derive cosmic microwave background (CMB) anisotropy constraints on non-Gaussianity, allowing us to make contact with those works. We find that the constraining power of the cluster survey on dark energy observables is not significantly diminished by non-Gaussianity, provided that cluster redshift information is included in the analysis. We also find that even an ideal cluster survey is unlikely to significantly improve current and future CMB constraints on non-Gaussianity. However, when all systematics are under control, such surveys could constitute a valuable cross-check on CMB observations.

Large Sunyaev-Zel'dovich-selected galaxy cluster surveys are beginning imminently. We compare the dependence of the galaxy cluster angular power spectrum on cosmological parameters, different modeling assumptions, and statistical observational errors. We quantify the degeneracies between theoretical assumptions such as the mass function and cosmological parameters such as s8. We also identify a rough scaling behavior of this angular power spectrum with s8 alone.

We explore the possibility that the annihilation of dark matter (DM) is boosted due to enhanced substructure in the presence of primordial black holes (PBHs) which constitute a subcomponent of DM. The PBHs can generate entropy fluctuations at the small scales which trigger early structure formation, and a large fraction of the whole DM can reside in these collapsed objects that formed at high redshift (z≳100). Such early forming minihalos consequently possess higher densities than those in the conventional scenarios (without PBHs) and would be more resilient to tidal disruptions. Our scenarios of the annihilation boost due to DM substructures are of particular interest for light (<1 GeV) DM which has been less explored compared to heavier DM in the presence of the PBHs. [ABSTRACT FROM AUTHOR]